Production of metal ingots, slabs and billets



United States Patent 14 Claims. (Cl. 164-33) ABSTRACT OF THE DISCLOSURE A method for the production of ingots of steel and slabs and billets of Cu, Ni and alloys of each that prevents the formation of oxidation defects, and comprises pouring a molten metal into a metal mold, characterised in that there is placed in the bottom of a mold, the walls of which are free from mold dressing, a tablet or a fused tablet of a carbocyclic chemical substance which comprises carbon and hydrogen, burning the substance not later than the pouring of the molten metal into the mold, with the substance on burning causing a non-oxidising, non-corrosive vapor and a deposit of carbon particles on the walls of the mold, the particles being adherent to the walls because of the adhesive action of material deriving from the substance.

This invention relates to the production of ingots by the method in which molten metal is poured into metal moulds and is particularly concerned with the production of ingots of steel or of slabs or billets of copper, nickel or alloys of either of these.

When pouring molten steel into metal ingot moulds there is a tendency towards the formation of an oxide skin on the surface of the stream of molten metal which is exposed to the atmosphere. Such oxide formation is more prevalent in the case of top-poured ingots since on striking the bottom of the ingot mould, or the rising surface of the poured metal, splashed metal impinges on the side walls of the mould and remains as flattened droplets with oxidised surfaces. Most of these oxidised droplets cannot be redissolved into the body of the molten ingot metal and remain to form defects and blemishes on the ingot skin and, possibly, inclusions in the body of the ingot. Similarly, oxide floating on the surface of the rising metal as the molten metal is poured into the mould may become trapped between the molten metal and the mould walls, giving rise to similar defects.

It is known to use mould dressings or mould additives which reduce oxidation of the molten metal by their fluxing or reducing action and thus help to prevent the above defects. For example, there are, on the one hand, slags, With a melting point considerably lower than that of the metal being cast, which form a molten fluxing layer on the rising surface of cast metal and, on the other hand, there are the commonly used types of mould dressing including those based on tar, pitch or heavy oil compositions. These latter produce the required reducing atmosphere but they give rise to the production of large quantities of smoke and soot during casting, besides being unpleasant and dirty in their application.

Analogous difiiculties arise in the production of slabs and billets of copper-based and nickel-based alloys.

It is an object of the present invention to provide means whereby excellentprotection, and in some cases complete protection, against the formation of oxidation defects in steel ingots, and copper-based and nickel-based slabs and billets can be achieved.

3,376,914 Patented Apr. 9, 1968 According to the present invention, therefore, there is provided a method for the production of ingots of steel or slabs or billets of copper, nickel or alloys of either which comprises pouring the molten said metal into a metal mould, characterized in that there is placed in the mould a carbocyclic chemical substance which comprises carbon, hydrogen and optionally also oxygen and/ or nitrogen and which will on burning cause a deposit of carbon particles on the walls of the mould, the said particles being adherent to the said walls by reason of the adhesive action of a portion of the said substance or of a combustion product of said substance which deposits on the walls of the mould by sublimation or condensation, or which exists as a coating on the carbon particles, the said substance generating, on burning, a non-oxidising non-corrosive gas or vapour, and burning the said substance to establish a said deposit prior to or simultaneously with the pouring of the said molten metal into the mould.

The substance may be a single organic chemical compound or mixture of such compounds. It has sometimes been found preferable to employ a substance which is a stable solid at temperatures up to about C. but, more particularly, remains solid at temperatures up to C. Alternatively, a substance which exists as a heavy gas at temperatures of 80 C. and above, but which is solid or liquid at room temperature, may be employed. If the selected substance has a melting point below 140 C. it is generally preferable that it should have a short-melting range, i.e. the temperature gap between its melting and boiling temperatures (at ordinary pressure) should be of the order of 30 C. or less.

The selected substance should preferably not be deliquescent or hygroscopic since such substances have a tendency to introduce water vapour into the mould. It is generally found preferable to employ an aromatic compound with a high proportion of carbon in the molecule.

A wide variety of compounds are suitable for use in carrying out the method of the invention. These include carbocyclic hydrocarbons such as naphthalene, phenanthrene, anthracene, biphenylene, naphthacene, rubrene, pentacene, heptacene, pyrene, perylene and acenaphthene. Other suitable substances are phenolic compounds (eg. resorcinol, hydroquinone, alpha and beta-naphthol, anthraquinone and quinol), esters of carbocyclic acids (e.g. pentaerythritol and glycerol esters of rosins, such as ester gum), terpene compounds (e.g. camphor, borneol, pinene or abietic acid, or certain natural or synthetic resins containing carboxylic groups (e.g. phenolformaldehyde, copal, terpene resins and alkyd resins) may be used. Nitrog enous compounds may also be used, e.g. u-naphthylamine and the aminoanthroquinones. Halogen-containing substances, aromatic acids and anhydrides are not preferred substances since they tend to cause corrosion.

The list of substances for use in the invention just set forth is not to be regarded as exhaustive since any organic carbocyclic substance which affords the desired coating of carbon particles and other effects as set forth may be employed. The efiiciency of any compound can be readily ascertained by simple test.

It has been found that extremely small amounts of such substances are sufiicient to give the desired effect. It is to be noted in this connection that when the same substances are included in sand moulds used for making castings an improvement in fluidity of the molten metal is achieved. This however usually requires a minimum proportion of the volatile substance of the order of 0.01% based on the molten metal being cast. In the present invention, which is concerned only with the casting of steel or copper based or nickel based metals, into metal chill moulds, still smaller quantities may be employed, i.e. quantities less than 0.01% and frequently as low as 0.002% or even less.

A preferred group of additives Within this range are those having the following compositions:

Parts by weight Ester gum 80-90 Resin (as aforesaid) 15-5 Carbon black -5 (B) Mixtures of camphor, and naphthalene, optionally also containing urea.

A suitable range of these ingredients is:

Parts by weight -95 Camphor Naphthalene 95-5 Urea 0-10 A preferred group of additives within this range are those having the following compositions:

Parts by weight Camphor 75-85 Naphthalene -20 Urea 0-10 A specific composition of this class is:

Parts by weight Camphor 80 Naphthalene 10 Urea 10 The substance may be used in powder or tablet form. However, it has been found that the physical condition of the additive has an important bearing on the results obtained, especially when the additive is used in the production of large ingots, e.g. ingots over 3 tons in weight. When dealing with large ingots there is sometimes a tendency for the additive, if used in powder or other divided form, to volatilise rather too rapidly so that its effects on the upper parts of the ingot are minimised. This difficulty is not readily overcome by the use of quantities of the additive localised at different heights in the mould but it has been found that satisfactory results can be obtained by using the additive in the form of a tablet, block or briquette. In this form the volatilisation of the additive is slowed down. To ensure the best results in the circumstances just outlined it is desirable that the tablet, block or briquette should have a bulk density closely approximating to the net density, or specific gravity, of the material or of its ingredients. Hence if a tablet, block or briquette is used which has been made by compressing the additive in a mould it is desirable that such high pressure should be used that there is little or no air included within the tablet, block or briquette.

When the additive is one which can be melted before volatilisation it is greatly preferred to employ the product in the form of a block-obtained by such a fusing operation since this tends to achieve a product of the highest available compactness. Moreover this method is especially valuable when the nature of the additive is such that it does not readily lend itself to the pressure-forming procedures.

Thus for example an additive of especial value is one 4 containing ester gum and phenol-formaldehyde resin e.g. in the following proportions: I

Parts by weight Ester gum 85 Phenol-formaldehyde resin 15 Such a composition cannot readily be tabletted but it can readily be melted and then cooled and the solidified product converted to blocks of convenient size.

In the state of fused blocks the rate of volatilisation is such that even on large ingots the material continues vapourising over the whole teeming period and thus the upper parts of the ingot have an improved surface WhlCh results from the use of such additives. The material, in fused block form, has a volatilisation time of approximately one and a half times that of the tabletted material and very much greater than that of the powdered material. In the form of fused blocks it is much more convenient to use and its handleability is considerably improved. The use of fused blocks also makes for greater economy as application of a predetermined amount 18 readily effected. Fused blocks can be used on any size ingot from the smallest upwards whereas powder and tablet additions are preferably only employed for ingots up to three tons in weight. The rate of addition may be the same for tablets as for powder but with fused blocks, smaller additions can sometimes be used. When using powder, multiple additions may be necessary throughout teeming but with fused blocks it is generally satisfactory to add the required quantity at the beginning of the teeming, the size of the block being such as to ensure that material remains available until the ingot mould is filled. Recommended additions are as follows:

For ingots up to 500 lbs., 2-4 oz. per ton.

For ingots of 500 lbs. to 5 tons, 4-10 oz. per ton.

For ingots above 5 tons, and on crusting steels, 6 oz. per ton.

In carrying out the method of the invention the required quantity of the substance is placed in the bottom of the metal ingot mould.

The substance may be ignited and allowed to burn before introducing the molten metal or alternatively the ignition may be effected by the introduction of the molten metal into the mould. The substance decomposes so that the mould is filled with its vapours or the vapours of its decomposition products and an adherent carbon deposit is formed on the walls. As the substances volatilise or decompose completely there is no possibility of experiencing the disadvantages peculiar to the previously known dressings, i.e. there is no possibility of inclusions in the cast steel deriving from the additive and there is no slag of any sort remaining on the surface of the cast metal. There is little or no fume problem. Furthermore, the simplicity of application compared to normal methods of applying mould dressings is a distinct advantage.

The invention can be usefully applied in the casting of ingots of all types of steel but is especially useful for alloy steels, ingots of dimensions varying from 3 square to 18" square (approx. lbs.-2 tons) having been treated with absolute success, by the use of powdered additives and ingots of 3 to 6 tons having been successfully treated with the fused block additives.

I claim as my invention:

1. A method for the production of ingots of steel and slabs and billets of copper, nickel and alloys of each which comprises pouring the molten said metal into a metal mould, characterized in that there is placed in the bottom of mould, the walls of which are free from mould dressing a tablet of carbocyclic chemical substance which comprises carbon and hydrogen and which will on burning cause a deposit of carbon particles on the walls of the mould, the said particles being adherent to the said walls by reason of the adhesive action of material deriving from said substance, the said substance generating, on burning, a non-oxidising non-corrosive vapour, and burning the said substance to establish a said deposit not later than the pouring of the said molten metal into the mould.

2. A method for the production of ingots of steel and slabs and billets of copper, nickel and alloys of each which comprises pouring the molten said metal into a metal mould, characterized in that there is placed in the bottom of mould, the walls of which are free from mould dressings a tablet of carbocyclic chemical substance which comprises carbon, hydrogen and oxygen and which will on burning cause a deposit of carbon particles on the walls of the mould, the said particles being adherent to the said Walls by reason of the adhesive action of material deriving from said substance, the said substance generating, on burning, a non-oxidising noncorrosive vapour, and burning the said substance to 5 establish a said deposit not later than the pouring of the said molten metal into the mould.

3. A method for the production of ingots of steel and slabs and billets of copper, nickel and alloys of each which comprises pouring the molten said metal into a metal mould, characterised in that there is placed in the mould a tablet of carbocylic chemical substance which comprises carbon, hydrogen and nitrogen and which will on burning cause a deposit of carbon particles on the walls of the mould, the said particles being adherent to the said walls by reason of the adhesive action of ma-- terial deriving from said substance, the said substance generating, on burning, a non-oxidising non-corrosive vapour, and burning the said substance to establish a said deposit not later than the pouring of the said molten metal into the mould.

4. A method for the production of ingots of steel and slabs and billets of copper, nickel and alloys of each which comprises pouring the molten said metal into a metal mould, characterised in that there is placed in the bottom of mould, the walls of which are free from mould dressings a tablet of carbocyclic chemical substance which comprises carbon and hydrogen and which will on burning cause a deposit of carbon particles on the walls of the mould, the said particles being adherent to the said walls by reason of the adhesive action of material deriving from said substance adherent to the said particles, the said substance generating, on burning, a non-oxidising non-corrosive vapour, and burning the said substance to establish a said deposit not later than the pouring of the said molten metal into the mould.

5. A method for the production of ingots of steel and slabs and billets of copper, nickel and alloys of each which comprises pouring the molten said metal into a metal mould, characterised in that there is placed in the 5 bottom of mould, the walls of which are free from mould dressings a tablet of carbocyclic chemical substance which comprises carbon and hydrogen and which will on burning cause a deposit of carbon particles on the walls of the mould, the said particles being adherent to the said walls by reason of the adhesive action of material deriving from said substance which also deposits on said walls, the said substance generating, on burning, a nonoxidising non-corrosive vapour, and burning the said substance to establish a said deposit not later than the pouring of the said molten metal into the mould.

6. A method according to claim 1 wherein the said substance includes naphthalene.

7. A method according to claim 1 wherein the said substance includes a compound of the terpene class.

8. A method according to claim 1 wherein the said substance includes camphor.

9. A method according to claim 1 wherein the said substance includes an ester of a carbocyclic acid.

10. A method according to claim 1 wherein the said substance includes ester gum.

11. A method according to claim 1 wherein the said substance includes a resin containing a carbocyclic groupmg.

12. A method according to claim 1 wherein the said substance includes an alkyd resin.

13. A method for the production of ingots of steel and slabs and billets of copper, nickel and alloys of each which comprises pouring the molten said metal into a metal mould, characterised in that there is placed in the mould a fused tablet of a carbocyclic chemical substance which comprises carbon and hydrogen and which will on burning cause a deposit of carbon particles on the walls of the mould, the said particles being adherent to the said walls by reason of the adhesive action of material deriving from the said substance generating, on burning, a non-oxidising non-corrosive vapour, and burning the said substance to establish a said deposit not later than the pouring of the said molten metal into the mould.

14. A method for the production of ingots of steel which comprises pouring the molten said metal into a metal mould, characterised in that there is placed in the bottom of the mould, the walls of which are free from mould dressings, in a proportion of 0.002 to 0.01% by weight of the steel cast, a tablet of carbocyclic chemical substance which comprises carbon and hydrogen and which will on burning cause a deposit of carbon particles on the walls of the mould, the said particles being adherent to the said walls by reason of the adhesive action of material deriving from the said substance generatin on burning, a non-oxidising non-corrosive vapour, and burning the said substance to establish a said deposit not later than the pouring of the said molten metal into the mould.

References Cited UNITED STATES PATENTS 3,216,078 11/1965 Zrimsek 164-56 3,138,836 6/1964 Amala 164-43 2,025,336 12/1935 Brearley l6459 2,923,041 2/ 1960 Ryznar 164-72 3,042,541 7/1962 Kaplan 117-5.3 3,037,873 6/ 1962 Ingala 117--5.3 1,536,952 5/ 1925 Meloche et al. 2,245,651 6/1941 Craig et al. 164-72 X 373,186 11/1887 Illingworth 16474 2,893,084 7/ 1959 Eisermann 164--67 3,158,913 12/1964 Bolkcom et al 16455 FOREIGN PATENTS 986,422 3/ 1965 Great Britain.

525,223 8/1940 Great Britain.

792,040 3/ 1958 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner. V. RISING, Assistant Examiner. 

